Diagnosis and Management of Adult-Onset Still's Disease (AOSD)

Diagnosis

The European League Against Rheumatism recommends AOSD diagnosis requires operational criteria focusing on four cardinal features: spiking fever, transient salmon-pink rash, musculoskeletal involvement, and high inflammation markers 1, 2
The American College of Rheumatology suggests fever pattern must reach ≥39°C with characteristic spiking pattern lasting at least 7 days 1, 2
The diagnosis is supported by rash characteristics: transient, erythematous, preferentially on trunk, often coinciding with fever spikes 1, 2
Musculoskeletal involvement, such as arthralgia/myalgia, is usually present, and overt arthritis may appear later 1, 2
Laboratory markers, including neutrophilic leukocytosis, elevated CRP, and markedly elevated serum ferritin, are typical 1, 2

The European League Against Rheumatism recommends IL-1 inhibitors or IL-6 receptor inhibitors as first-line treatment, with the highest level of evidence for efficacy 1, 2, 3
For active AOSD, start with IL-1 inhibitor or IL-6 receptor inhibitor immediately, with anakinra preferred if macrophage activation syndrome is impending 1, 2, 3
Early initiation of biologic therapy improves outcomes due to a "window of opportunity" before 3 months of symptom onset 4

The ultimate goal is drug-free remission, defined as at least 6 months of clinically inactive disease without medications 1, 2, 3
Sequential treatment targets include resolution of fever and CRP reduction >50% by day 7, and no fever, active joint count reduction >50%, normal CRP, and physician/patient global assessment <20 on 0-100 VAS by week 4 1

Macrophage activation syndrome should be detected promptly and treated rapidly, with high-dose glucocorticoids and anakinra 1, 2, 4
Lung disease should be actively screened for with clinical symptoms and pulmonary function tests, and IL-1 or IL-6 inhibitors are not contraindicated in patients with lung disease 1, 2

AOSD follows three clinical patterns: monocyclic/self-limited, polycyclic/intermittent, and chronic articular, each affecting approximately one-third of patients 3
Prednisone requirements increase with disease pattern, with 57% for self-limited, 67% for intermittent, and 77% for chronic articular AOSD 5

Never rely solely on NSAIDs or glucocorticoids as long-term therapy, as 85-93% of patients will require more advanced treatment 5, 6, 3
Avoid maintenance prednisone 10-15 mg/day for arthritis, as it can lead to severe joint destruction 6, 4
Do not delay biologic therapy beyond 3 months of symptom onset, as early initiation prevents persistent chronic course 4
Maintain high suspicion for macrophage activation syndrome throughout disease course, as it can develop at any time 1, 4